Electron discharge devices



March 12, 1957 D. B. HAAGENSEN 2,785,380

ELECTRON DISCHARGE DEVICES Filed June 501955 /fugmm Bv MM 32?* A T RNEY i i l United States Patent ELEcrRoN DISCHARGE DEVICES Duane B. Haagensen, Wayland, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application January 30, 1953, Serial No. 334,214

2 Claims. (Cl. S32- 5) This invention relates to electron discharge devices and more particularly to an improved form of microwave generators of the magnetron type.

It is well known that magnetron oscillators may be constructed which will produce high microwave power with relatively high eciency. However, vdifliculty has been encountered in modulating these devices, both in frequency and in amplitude. In the case of amplitude modulation this has previously been accomplished by varying the anode voltage. However, this requires a large modulating power and also is unsatisfactory where it is desired to produce wide band frequency modulation, since the frequency response of the high power anode modulator is relatively low.

This invention discloses that a grid-controlled magnetron may be used to produce amplitude-modulated microwave energy by varying the bias of the grid as a function of the modulation signal and by coupling to the grid an external source of microwave energy whose frequency lies in the operating range of frequencies of the grid-controlled magnetron, whereby the frequency of the grid-controlled magnetron will be stabilized by the external source during amplitude modulation.

This invention further discloses that a grid-controlled magnetron may be frequency modulated by coupling the grid to an external source of microwave energy and by frequency modulating the external source.

Other and further objects and advantages of this invention will be apparent as the description thereof progresses, reference being had to the drawing wherein the single figure illustrates a partial block diagram and partial structural illustration of a system embodying the invention.

Referring now to the drawing, there is shown a gridcontrolled magnetron 1 having an anode structure cornprising an outer anode cylinder 2, which may be made of conductive material, such as copper. Extending radially inwardly from the anode cylinder 2 are a plurality of anode members 3, which are alternately connected on their upper edges adjacent their inner ends by a pair of conductive straps 4. An output coupling device 5 comprising an inductive loop is positioned between two of the anode members 3 near the anode cylinder 2 and extends out through an output coupling seal 6 attached to the anode cylinder 2 to feed an output load 7.

Positioned in the space defined by the inner ends of anode members 3 is a cathode 8, which is rigidly attached to a cathode support 9. The cathode support 9 extends outwardly through a lower magnetic pole piece 10, sealed to an aperture in a lower cover plate 11, which, in turn, is sealed to the lower end of anode cylinder 2. Positioned inside cathode support 9 is a heater lead-in member 12, which extends upwardly into cathode 8 and is connected to one end of a heater coil, according to well-known pracf tice. Insulating seals (not shown) are provided between members 9, 10, and 12, according to well-known practice.

The upper end of anode cylinder 2 is sealed to an upper cover plate 13 through which extends an upper magnetic pole piece 14. A magnetic field is impressed between the magnetic pole pieces 10 and 14 by means of a magnet, shown at 15.

A plurality of grid elements 16 are positioned substantially equidistant between the anode members 3 adjacent their inner ends, grid elements 16 being positioned somewhat farther from the cathode 8 than the tips of the anode members 3. The grid elements 16 are rigidly attached to a support plate 17. Support plate 17, in turn, is attached to a lead-in member 18, which extends outwardly through an aperture in upper magnetic pole piece 14, said aperture being closed by insulating seal 19. Lead-in member 18 is connected to the inner conductor 20 of a coaxial line 21, whose outer conductor 22 threadedly engages the aperture in upper magnetic pole piece 14 outside the seal 19.

A microwave locking oscillator, which may be, for example, of relatively low power, such as a conventional reex klystron 23, is coupled through a coaxial phase ad juster and attenuator 24 to the coaxial line 21 and thence to the grid elements 16 of the magnetron. The coaxial phase adjuster and attenuator is shown here diagrammatically and in practice, the phase adjuster may be a coaxial line, which may be lengthened or shortened by means of sliding inner and outer conductors and the attenuation may be obtained by variably inserting lossy material into the coaxial line. Power for the oscillator 23 is supplied from an oscillator power source 25.

If desired, the frequency of the microwave locking oscillator 23 may be varied by means of a frequency modulator 26. This may be accomplished, for example, in the case of a reflex klystron by varying the repeller voltage, which, in turn, varies the output frequency. It has been found that, if the frequency of the microwave oscillator is substantially at the normal operating frequency of the magnetron 1, the magnetron will lock on the frequency of the microwave oscillator 23, and, hence, the frequency of the output 7 will be independent of variations of the bias applied to the grid elements 16 of the magnetron 1, or the anode voltage applied to the magnetron 1, or other disturbances, such as mechanical shock applied to the magnetron 1.

If the frequency of the microwave oscillator 23 is varied over a relatively wide range, for example, several megacycles, by the frequency modulator Z, the output frequency of the magnetron 1 will follow the frequency of the microwave oscillator 23, and, hence, the output of the magnetron 1 will be frequency modulated in accordance with the modulation signal input to the frequency modulator 26. The output of the grid control magnetron 1 may be amplitude modulated by applying a modulation signal directly to the grid elements 16. This is accomplished, for example, by connecting a grid modulator 27 through the coaxial phase adjuster and attenuator 24 and the central conductor Ztl of the coaxial line 21 to the grid elements 16.

An average biais for the Agrid 16 is provided by a battery 28 connected between the cathode support member 9 and the grid modulator 27. Anode voltage for the magnetron 1 is provided by means of a battery 29 connected between the anode structure of the magnetron and the cathode support member 9. Thus it may be seen that, by holding the frequency of the microwave locking oscillator 23 constant, the microwave output of the magnetron l may be made to vary in amplitude in accordance with the amplitude modulation input signal applied to the grid modulator 27, while the frequency of the output of the magnetron 1 remains constant. lf desired, modulation signals may be simultaneously applied to both frequency modulator 26 and the grid modulator 27 so that the outwas@ put of the magnetron 1wi-l-l have (bot-h frequency and amplitude modulation components.

The coaxial phase adjuster is adjusted such that the grid load impedance ofthe magnetron Lreected' to the microwavevoscillator 23, is the desired load impedance for osci-llator 23 and the attenuator is adjusted so that the reactive components of the magnetron grid impedance will riot severely shift or vary the Yfrequency of the oscillator 23.

The vspeciiic details of the grid control magnetron 1 are more completely described in my copending application, Serial No. 257,830, filed November 23, 1951, now Patent No.'2,748,277, dated May 29, 1956.

This completes the description of the specic embodiment of the invention disclosed herein. However, many modifications thereof will be apparent to persons skilled in the art without departing from the spirit and scope of this the frequency modulator 26 and gridV modulator 27 may be simple signal sources, amplifiers, or buffers asV desired. Accrdingly, it is desired that this invention be not limited by the particular details of the species of the invention illustrated and described herein, except as defined by the appended claims.

What is claimed is:

l. In combination, an electron discharge device comprising a signal wave transmission network having an operating frequency range, means for directing electrons along paths adjacent said network, a grid positioned adjacent said network, means for maintaining the frequency of said discharge device at a predetermined value lying within said operating range including means for supplying said grid with microwave energy from an external source whose frequencyis of said predetermined value, and means for varying the frequency of operation of said discharge device in response to a modication of the characteristics of said microwave energy, said means for varying including means for frequency modulating said microwave energy, and means for varying the amplitude of the output of said discharge device in accordance with a variable amplitude input signal applied to said grid. u

2. An electron discharge device comprising a signal wave transmission network having anoperating frequency range, means for directing electrons along paths adjacent said network, a grid positioned adjacent said network substantiallyoutside of but unshielded'from'said paths', means for maintaining the frequency o f said 4discharge system at a predetermined value lying/within said operating range including means for supplying said grid With microwave energy from an external -source whose yfrequency is of said predetermined value, 'means for altering the frequency of operation of said dischargel device in4 response to a modification of the characteristics of said microwave energy, said means for altering including means for frequency modulating said microwave energy, and means orvarying the amplitude of the outputof said discharge device in accordance with a'variable 'amplitude input signal applied t0 said grid.

References Cited in the tile of this patent UNITED STATES PATENTS 

